What is a TBC? Time Base Correction for Videotapes

[WaxCyl]

Quote:

Originally Posted by msgohan

You can when none of your sources come close to having full chroma resolution. Do you really think your home recordings using consumer equipment have more chroma resolution than, say, a 4:2:2 studio master made from a 35mm film scan in 1990 or 2005 simply because your recordings are stored on analog tape?

No of course not! This is a personal choice though. I would also choose to Capture my analog cassettes in FLAC format not MP3! I dont want to add MP3 losses to an already bad recording!
(Actually it is probably unfair to compare MP3 with 4:2:0)

Quote:

Originally Posted by msgohan

The process of color-under recording itself is a form of lossy analog compression that massively cuts down the chroma resolution and is the reason for color bleed on tapes in the first place.

Yes I know this! I think the Hi-8/VHS chroma resolution is only about 80 lines.(?)
I have noticed that 4:2:0 capture slightly worsens already bad chroma

Quote:

Originally Posted by msgohan

Basically any decent capture chip since like 1998 internally samples at 1440 or greater and downsamples to the specified output resolution.

Yes great. But don't you think it would be more logical to downsample to 768 and not re-up 720 to 768?

Quote:

Originally Posted by msgohan

It's worth noting that unless you turn off the TBC in your S-VHS or Hi8 player, you've already converted your video to 8-bit 4:2:2 (or less) before it has the chance to reach your 10-bit converter. So you are giving yourself more headroom for your second A-D step, but the signal has already been limited. Even the TBCs in Betacam SP decks were only 8-bit.

I have more or less acknowleged this above.

Nevertheless it is a pleasure to talk to someone that knows what I am talking about..

[msgohan]

Quote:

Originally Posted by WaxCyl

Yes great. But don't you think it would be more logical to downsample to 768 and not re-up 720 to 768?

If you were displaying at 768, but aren't you displaying on an HDTV? Taking your 720 capture and having it resized by integer 2 to get 1440 horizontally is then better than 1.875. (Unfortunately the same isn't possible vertically.)

[EDIT: I see you're scaling to 960x720. So unless you're playing that windowed or have a display that is really 720p and not one of those 768p panels, there's an extra resizing step added.]

Quote:

Nevertheless it is a pleasure to talk to someone that knows what I am talking about..

If you have used it much, could you post your thoughts about the DPS-575 in that thread linked earlier?

[lordsmurf]

Quote:

Originally Posted by WaxCyl

Nevertheless it is a pleasure to talk to someone that knows what I am talking about..

It's a pleasure to read educated debates.

[WaxCyl]

I first resize to 960x720 (4:3) and then add sidebars to 1280x720 50p (BD).
Downscales lose data but multiple upscales are probably harmless.
My plasma is 1920 x 1080 but I choose 720 so that I can get 50FPS
Yes it will be interesting to compare DPS575.
If I am to to do a cartoon source I need my SVHS machine.
The one with LTBC is out of action for the time being

[msgohan]

Ideally, you would try to eliminate extra upsize steps in the same way that you would try to reduce the number of YUV/RGB conversions.

So is the idea just that you want 50fps files you can burn to disc instead of connecting a hard drive to a media player? Have you ruled out using the AVCHD 2.0 spec for 1080p50?

[WaxCyl]

More thoughts:
Since 1440 rez is really anamorphic 1080 x 1920 why not use this?.
Currently NNEDI3 upscales X2 but I am then downscaling back to 720, instead I could upscale to 1080.
My workflow could be 1080 x 1920 50p. Bluray can't take this resolution but I could put it in an MKV format for viewing on my TV. I think my Cambridge player can handle this.

Our thoughts are simultaneous!!
Can I put AVCHD on a Bluray disc?
I think maybe not all players handle AVCHD?

[msgohan]

You might consider checking if your MKV player works with 576p50 and comparing its own upscaling to NNEDI3. I prefer not to bake upsizing into my encodes at all.

Quote:

Originally Posted by WaxCyl

Since 1440 rez is really anamorphic 1080 x 1920 why not use this?.

Well, because it is anamorphic 16:9. So that's another unnecessary resize step to stretch from 1440 to 1920 on playback.

Quote:

Originally Posted by WaxCyl

Can I put AVCHD on a Bluray disc?
I think maybe not all players handle AVCHD?

Yes to both questions. You would need a player that works with the 2.0 revision of AVCHD, specifically.

[Zerowalker]

Hmm i thing i thought about.
Does capturing in Full Range increase quality in this case?

You make adjustments so the Black is Black and White is White etc in Full Range.
This should increase the quality a bit compared to TV standard, as i don't actually thing this is set in stone when it's analogue.

-- merged --

Other than my previous question.

I would like to know if there are some images from TBC-100?
As all the other seems to have negative impact in some way that's noticeable (resolution,bleeding etc).

Also, i don't quite grasp the need of a TBC when you can still get it without it.
Meaning, many Capture Cards can't capture VCR content cause of the instable signal,
but some can. And in those cases, are TBC really needed, what does it to there?

[msgohan]

Quote:

Originally Posted by Zerowalker

Does capturing in Full Range increase quality in this case?

You make adjustments so the Black is Black and White is White etc in Full Range.

Technically yes, because you have 256 values available instead of 220. But you shouldn't do it, because you're going against the standards and creating a video that will only be displayed properly using a specially tweaked pipeline.

[Zerowalker]

True, but wouldn't it also increase quality in the end result (like 10bit to 8bit would)?
Though obviously a lot less compared to a bit increase.

[volksjager]

Quote:

Originally Posted by Zerowalker

Also, i don't quite grasp the need of a TBC when you can still get it without it.
Meaning, many Capture Cards can't capture VCR content cause of the instable signal,
but some can. And in those cases, are TBC really needed, what does it to there?

to help prevent dropped frames

[Zerowalker]

But if i don't get dropped frames?
Normally when i capture with such a card (which in this case would be a conextant card, which sadly can't handle contrast/brightness well which makes it useless for archival "White Crush"*), i don't get dropped frames, except for example if the tape is Empty and then it switches to having content, that Switch can cause some dropped frames as it's just garbage, but i don't think that matters at all as it's nothing of interest there and just duplicating frames suffice.

*White Crush is some kind of function it has that is supposed to prevent contrast from crushing colors.
Sadly it's just weird, it will simply darken the picture (dynamically), and the white can still crush information.
So it's like you would increase contrast on a picture, then reduce it afterwards.

[msgohan]

Quote:

Originally Posted by Zerowalker

True, but wouldn't it also increase quality in the end result (like 10bit to 8bit would)?
Though obviously a lot less compared to a bit increase.

It's not worth making incompatible video for such a small gain. Video is complicated enough as it is without deliberately breaking things.

[Zerowalker]

I wouldn't be incomatible. I meant,

Capture = 0-255 Full Range -> Lossless

Restore/Filter the clip and most likely upsample to 16bit.
Convert to 8bit 16-235 in the end.

[WaxCyl]

Quote:
Originally Posted by Zerowalker View Post
True, but wouldn't it also increase quality in the end result (like 10bit to 8bit would)?
Though obviously a lot less compared to a bit increase.[/quote]

Quote:

Originally Posted by msgohan

It's not worth making incompatible video for such a small gain. Video is complicated enough as it is without deliberately breaking things.

Maybe Zerowalker has a point. Maybe he could capture at 0-255 , do his video processing and then resquish down to 16-236. Could this be a slight improvement in workflow? It certainly would not be as great a gain as 10 bit processing. Also , it could make things worse for YUV <> RGB conversions due to out of gamut colors being generated.

Quote:

Originally Posted by Zerowalker

Other than my previous question.

I would like to know if there are some images from TBC-100?
As all the other seems to have negative impact in some way that's noticeable (resolution,bleeding etc).

Also, i don't quite grasp the need of a TBC when you can still get it without it.
Meaning, many Capture Cards can't capture VCR content cause of the instable signal,
but some can. And in those cases, are TBC really needed, what does it to there?

I later discovered identical frames in old analog to DV captures, This means the Canopus unit was adding and presumably dropping frames due to a lack of TBC.
This is what set me on a quest for a TBC

[Zerowalker]

Not sure what you mean.
Are you saying your capture card would capture without issue. But instead going black, it would duplicate frames instead?

Cause this doesn't happen to me with Conextant as far as i can tell. There should be no identical frames (except the ones added by VirtualDub when needed, which mostly is in those "empty tape/Swich scene" scenarios).

[WaxCyl]

Yes, sorry, the dupe frames are probably added by the capture software.
Nevertheless this would not happen if a TBC is used

[Zerowalker]

Well my Webcam produces a lot of dups (in VD) cause of it not giving a flawless stream of frames.
It's "30fps" is actually about "28.874fps", this may probably differ depending on PC clock.

However, not sure how it is for Capture card with TBC, will they produce 25.00000 fps?
I somehow doubt this is possible. But it should of course be much more stable compared to if the Capture card couldn't handle the "frames" which would makes the fps wiggle up and down.

[msgohan]

Quote:

Originally Posted by Zerowalker

Capture = 0-255 Full Range -> Lossless
Restore/Filter the clip and most likely upsample to 16bit.
Convert to 8bit 16-235 in the end.

In what way do you propose this would be better than setting black at 16 and white at 235 in the first place?

[Zerowalker]

You would be able to capture that 0-16 + 235-255 information in the first place.
Meaning you get more information during the capture.

Though, i guess it also depends on how the Capture card works. I have no idea how it does things, but if it just capture YUV and don't care if it's PC or TV range than this will make it able to Not truncate those values.